Contact-type Surface Roughness
In contact-type instruments, the stylus top makes direct contact with the surface of a sample. The detector tip is equipped with a stylus, which traces the surface of the sample. The vertical motion of the stylus is electrically detected. The electrical signals go through an amplification and digital conversion process to be recorded.
To precisely measure delicate shapes and roughness with a contact-type surface roughness tester, the radius of the stylus tip must be as small as possible with small contact pressure.
Styluses are made of sapphire or diamond and their tip radius is usually about 10 μm or smaller. A conical shape with a ballpoint tip is considered ideal for a stylus.
Tip radius: r tip = 2 μm, 5 μm, 10 μm
* Cone taper angle: 60º, 90º
* Unless otherwise specified, cones on ideal measuring instruments have a 60º taper.